CAN YOU BREATHE your way to lower blood pressure? That’s the claim behind a special biofeedback device called Resperate as well as other methods – including personal instruction, audiotapes and yoga-that employ slow, deep rhythmic breathing exercises.

It’s estimated that 50 million Americans-including more than two-thirds of those over 65-have high blood pressure, or hypertension, de-fined as readings of 140/90 mmHg or higher. Those with pressures below this level but above 120/80 have what’s known as prehypertension. The higher your blood pressure, the greater the risk of heart attacks, strokes and kidney disease. Most patients need two or more medications to lower their pressure adequately.

Mounting research shows that exercises to slow breathing can help reduce elevated blood pressure. The latest study, in this month’s Journal of Hypertension, found that breathing exercises can lower readings somewhat in people with mildly elevated pressure, whether or not they’re on blood-pressure medication. Other research, in patients whose pressure isn’t adequately con-trolled with medication, has shown greater reductions. Overall, those with higher pressure seem to benefit more, as do older people.

Though both stress and relaxation have long been known to affect blood pressure, at least temporarily, there’s no consensus on exactly why slower breathing appears to lower it. One theory is that it sends signals to the brain that cause muscles around blood vessels to relax, allowing blood to flow more easily.

Normally, we take 14 to 19 breaths a minute while at rest. The goal of slow-breathing programs is to lower the rate to under 10. One way to do this is with the Resperate de vice, which consists of headphones and a sensor that measures breath-ing. It emits tones that guide the user when to inhale and exhale. The device, which is approved by the Food and Drug Administration, is supposed to be used for 15-minute sessions at least three times a week. Manufactured by InterCure, it’s avail-able through the Internet for $299. Insurance doesn’t cover the cost.

Though Resperate can make the exercises easier and motivate you to stick with them, it’s not essential. One study showed that people with hypertension could learn to slow their breathing after just one lesson from an instructor. A yoga class or audiotape can also work. Whatever the method, it is important to learn how to do the exercises properly be-cause incorrect technique can raise pressure by causing you to tense up.

For the effects to continue, the exercises must be done regularly. To date, the longest follow-up has been only six months, so it is still not known whether exercises can lower pressure long-term or reduce the risk of heart disease and stroke, as medications do.

Some experts say breathing exercises may be worth trying especially if you have prehypertension and are trying to avoid medication, or if drugs fail to bring down your pressure enough. But be sure to discuss it with your doctor, and don’t stop your medication.